我可以重写SqlCommand函数吗？

Question

我的代码，这将是例如

Dim cmd As New SqlClient.SqlCommand(commandString, databaseString) 
Dim result As Integer 

Try 
    result = cmd.ExecuteScalar() 
Catch e as Exception 
    'catch exception code 
End Try 

而不是这样做，我可以重写的ExecuteScalar函数来完成某种通用的异常捕获的？

Answer 1

没有，但你可以创建一个通用的DoExecuteScalar辅助函数接受一个SQL字符串和连接字符串：

Public Function DoExecuteScalar(commandString as String, databaseString as String) as Object 
    Dim cmd as New SqlClient.SqlCommand(commandString, databaseString) 
    Dim result as Integer 
    Try 
     result = cmd.ExecuteScalar() 
    Catch e As Exception 
     Return 0 
    End Try 
    Return result 
End Function 

Answer 2

不，你不能覆盖方法，因为你不能从它继承自SqlCommand是sealed。

在使用SqlCommand时捕捉（或抛出）异常有什么问题？

Answer 3

您还可以使用组成：

Public Class SqlCommandManager 
Private _sqlCommand As System.Data.SqlClient.SqlCommand 
Public Sub New(command As System.Data.SqlClient.SqlCommand) 

    If command Is Nothing Then 
     Throw New ArgumentNullException("command") 
    End If 

    _sqlCommand = command 
End Sub 
Private ReadOnly Property Command As System.Data.SqlClient.SqlCommand 
    Get 
     Return _sqlCommand 
    End Get 
End Property 
Public Function ExecuteScalar() As Object 
    Dim result As Object 

    Try 
     result = Command.ExecuteScalar() 
    Catch e As Exception 
     'catch exception code 
    End Try 

    Return result 
End Function 
End Class 

不是说这是最好的选择，只是它是一个....